In many construction applications, like roofing, flooring, pond liners, insulation, decking, and other flat layered structures, adhesives are employed to affix layers together. For example, in large, flat commercial roof decks, the roofing substrate is a concrete, light weight concrete, wood, gypsum, wood fiber or steel roof deck. In other construction applications like flooring, the substrates are tile floors, carpeting, vinyl floors or wood floors. In roofing, a common material is the water proofing membrane that is used to seal and protect the roof deck from environmental weather conditions and is placed over insulation boards, which provide insulative qualities. The insulation boards are typically secured to the roofing substrate or roof deck via an adhesive composition or fasteners. The roofing membrane may be made of various materials, such as polymeric materials including EPDM (ethylene propylene diene M-rubber), Mod Bit (Modified Bitumen), TPO (thermoplastic polyolefin), or polyvinyl chloride (PVC). The roofing membrane may also be a composite material that includes EPDM or TPO. The roofing membrane is adhered overtop insulation boards or panels using an adhesive composition such as mopping asphalt (typically Type III or Type IV) or other conventional adhesive compositions. Conventional adhesives normally are required to be applied to both the roofing membrane and the substrate.
Adhesives are typically dispensed in a bead form which lends to poor and inefficient distribution of the adhesive. This method typically results in excess use of adhesive which is costly and the uneven application leads to an undesirable finish on the roof Other application methods as spray yield a more even coating but require special personal protective equipment during the application.
A conventional adhesive composition used to adhere the roofing membrane to the roof deck or other substrate includes the use of an elastomer dissolved in solvent, such as, for example, a polychloroprene rubber in an acetone or toluene solvent. Other adhesives are based on waterborne emulsions of polychloroprene rubber However, while useful for their intended purpose, these water based adhesives may have issues regarding temperature restrictions, long curing times, odor concerns and freeze-thaw stability. In addition, these adhesives are contact adhesives that require full coverage between the substrate and the membrane. Accordingly, solvent and water based elastomer adhesives must be applied to both the substrate and the roofing membrane and cover substantially the entire surfaces of the adhering components. These adhesives can blister when used between two non-breathable surfaces due to the incomplete evaporation of solvent or water from the above adhesives. For example, blistering may occur on a new roof membrane when applied over an existing roof membrane in recover applications. These adhesives are typically applied by pouring them on the roof and squeegeeing them across the surface or using a mop.
Accordingly, there is room in the art for adhesive compositions and distribution apparatuses that dispense such compositions with improved quality in roofing applications.